Five hundred draws are made at random with replacement from a box of numbered tickets; 276 are
positive. Someone tells you that 50% of the tickets in the box show positive numbers. Do you believe
it? Answer yes or no, and explain.
50% positive
50% negative
n=500
E(pos) = 250
(267/500) = 55,2% => 5,2%
SE = sqrt(0.25)/sqrt(500) = 0.5 * 1/sqrt(500) = 2.24%
z = 5.2%/2.24% = 2.33
p = P[2.33] = 0.9901 < 1% -> significant